This invention relates to a process for producing ammonia and hydrogen chloride using ammonium chloride as a raw material.
It is becoming an important industrial theme to recover ammonium and chlorine gas or hydrogen chloride in case using ammonium chloride as a raw material. In this regard, a decomposition process of ammonium chloride in the presence of a catalyst of an oxide of metal such as manganese or magnesium has been already proposed as a method for producing chloride gas or hydrogen chloride, not accompanying with the production of sodium hydroxide, which is particularly advantageous from a point of view of balance between sodium hydrogen oxide and chlorine. However, in this process, reactions are carried out by treating solids and therefore the following various problems have been encountered: a high reaction temperature above 500.degree. C. is required, and additionally it is difficult to obtain an effective heat-transfer surface. Accordingly, the catalyst will sublimate and disperse under the action of high temperature, and piping will be clogged with the deteriorated and partially fused catalyst.
Otherwise, the production of the hydrogen chloride and ammonia is carried out as follows: ammonium chloride and sodium hydrogen sulfate are mixed and heated to produce hydrogen chloride according to an Equation 1, and thereafter the reaction temperature is further raised to produce ammonia according to an Equation (2). EQU 2NH.sub.4 Cl+2NaHSO.sub.4 .fwdarw.(NH.sub.4).sub.2 SO.sub.4 +Na.sub.2 SO.sub.4 +2HCl (1) EQU (NH.sub.4).sub.2 SO.sub.4 +Na.sub.2 SO.sub.4 .fwdarw.2NaHSO.sub.4 +2NH.sub.3 ( 2)
However, since the melting points of sodium hydrogen sulfate and sodium sulfate are 315.degree. C. and 800.degree. C., respectively, the reaction of the Equation 1, or the reactions of the Equations 1 and 2 in this process are carried out in solid phase. Accordingly, the contact of the reaction products does not seem effective and therefore it is very difficult to completely carry out the reactions. Additionally, since the reaction of the Equation 2 is carried out at a temperature in the vicinity of the sublimation temperature of ammonium chloride, unreacted ammonium chloride at the Equation 1 sublimates as gaseous ammonium chloride which will be mixed into ammonia gas at the Equation 2. Recovering the thus mixed gaseous ammonium chloride is disadvantageous from a point of view of simplification of an apparatus for the reactions. Furthermore, the gaseous ammonium chloride attaches onto the inner surface of a upper section of a reactor, which becomes a cause of trouble. Moreover, if a larger amount of unreacted ammonium chloride is present, heat loss becomes greater by the amount corresponding to the amount of unreacted ammonium chloride. This is considerably disadvantageous from a stand point of thermal efficiency.